Hello there, the thread tittle made me curious. That's because I've encountered the same problem about 3-4 years ago, and it really bothered me.
Whenever I came home from doing minor work, or going somewhere for a few hours I'd be very tired. I was so tired that actually doing something was terribly hard even though I was fighting it.
However, I don't remember the impact on my brain as there was most likely none.

I don't recommend going to the doctor and trying to solve it on your own. This is because you've already stated where you're from and that the health care there isn't good. I'm not exactly sure what solved it for me, and there most likely won't be a instant solution for you either. Back then I've changed from no training at all to training 20 hours per week and with training comes a good diet (healthy meat, fish, vitamins, fruit, certain vegetables). I'm pretty sure that this is most likely going to fix your condition unless it is something more serious (which I doubt since you haven't described any other symptoms).

The problem is that humans were designed to move (not necessarily train, but just move). I'm assuming that you're spending a lot of time sitting on your computer and whatnot (just as I am right now), correct?. This is actually very dangerous in the long term, especially for office workers.